Formation of Irida-β-ketoimines and PCN amine -Ir(III) Complexes by Reacting Irida-β-diketones with Aliphatic Diamines: Catalytic Activity in Hydrogen Release by Methanolysis of H 3 N-BH 3

Aliphatic diamines [(H N(CH ) NHR) ( ) = 2: R = H ( ), R = CH ( ), R = C H ( ), = 3, R = H ( ) or -2-(aminomethyl)piperidine ( )] react with [IrH(Cl){(PPh ( -C H CO)) H}] in THF to afford ketoimine complexes [IrH(Cl){(PPh ( -C H CO))(PPh ( -C H CN(CH ) NHR))H}] ( - ) or [IrH(Cl){(PPh ( -C H CO))(PPh ( -C H CNCH (C H NH)))H}] ( ), containing a bridging N-H···O hydrogen bond and a dangling amine. Complex consists of an almost equimolar mixture of two diastereomers. In protic solvents, the dangling amine in complexes displaces chloride to afford cationic acyl-iminium compounds, [IrH(PPh ( -C H CO))(PPh ( -C H CNH(CH ) NHR))]X ( - , X = Cl) or [IrH(PPh ( -C H CO))(PPh ( -C H CNHCH (C H NH)))]Cl ( ) and ( - , X = ClO ), with new hemilabile terdentate PCN ligands adopting a facial disposition. Complexes contain the corresponding phosphorus atom trans to hydride and the amine fragment trans to acyl, while complexes contain the amine to hydride. and consist of 80:20 and 95:5 mixtures of diastereomers, respectively, while contains a 65:35 mixture. In the presence of KOH, intermediate cationic acyl-iminium complexes transform into neutral acyl-imine [IrH(PPh ( -C H CO))(PPh ( -C H CN(CH ) NHR))] derivatives ( ) with retention of the stereochemistry. Single-crystal X-ray diffraction analysis was performed on , [ ]Cl, [ ]Cl, [ ]ClO , and . Complexes , , and catalyze the methanolysis of ammonia-borane under air to release hydrogen. The highest activity is observed for ketoimine complexes .